The invention relates to a vehicle body having an underbody structure and an auxiliary frame which is fastened to the latter and bears components of a wheel axle of the vehicle. With regard to the prior art, reference is made by way of example to DE 10 2011 051 481 A1, in addition to WO 00/66417.
Two-track motor vehicles customarily have axle supports (=auxiliary frame), to which the wheel-guiding links and/or further elements of the respective vehicle axle are fastened. A precise and defined guidance of the wheels with realization of special kinematic and elastokinematic variables is crucial here for a good driving performance of the vehicle. In the case of modern and high-quality axles, a large portion of the development work is focused on the optimum resolution of the conflict of objectives between traveling comfort and precise wheel guidance. An essential step here is the acoustic insulation of the structure-borne sound transmission between the wheels or a transmission mounted in the axle support and the body via rubber bearings (=elastomer bearings), preferably via a multiply elastic mounting. In physical terms, the jump from a structure, for example the underbody structure, to the elastomer material of the rubber bearing constitutes a massive jump in rigidity, and this large jump in impedance causes structure-borne sound reflection and therefore only a small portion of the sound energy is transmitted. The wheel-guiding links are mounted elastically with coordinated elastokinematics on the auxiliary frame and the auxiliary frame is customarily mounted elastically on the underbody structure of the vehicle in order to reduce the structure-borne sound transmission or to obtain a defined load introduction. According to the prior art, the rubber bearing/elastomer bearings are mostly screwed or pressed in in the form of rubber/metal connections.
In recent times, use has increasingly been made of fiber composite materials. Even in the case of such auxiliary frames for example of CFRP, the above-described function of the rubber bearings is required. The joining of rubber bearings (for example via screwing or pressing in) causes a punctiform introduction of force into the structure or underbody structure and direct screwing to or on a fiber composite matrix is mostly not possible because of the settling behavior. Use is therefore customarily made of inserts made from metal in order to realize screw connections and to permit force to be introduced into the fibers; the joining or connecting technique for the rubber bearings results in technically complicated constructions.
It is the object of the present invention to provide a measure for remedying the above described problems.
The achievement of this object, for a vehicle body having an underbody structure and an auxiliary frame which is fastened to the latter and bears components of a wheel axle of the vehicle, is characterized in that the auxiliary frame is connected to the underbody structure without the interconnection of elastomer bearings or the like via a plurality of adhesive beads. The adhesive beads are configured not only in respect of a connection which satisfies the mechanical requirements, but, in particular in respect of the thickness thereof, also with regard to acoustic insulation. The auxiliary frame is supported, with the interposition of an acoustic insulating layer, on a securing structure provided below the auxiliary frame, which securing structure is connected to the underbody structure non-positively or in an integrally bonded manner. Advantageous embodiments and developments are further described herein.
It is therefore proposed no longer to fasten a chassis auxiliary frame to the vehicle body or to the underbody structure thereof as customary via rubber bearings or the like by means of screws, but rather to adhesively bond the auxiliary frame to the underbody structure, wherein adhesive beads which are suitable and are sufficiently thick or high—in respect of a joining gap between the auxiliary frame and the underbody structure—are provided as an accumulation of a suitable adhesive. These adhesive beads not only produce the mechanical connection, but also represent the acoustic insulating function of the hitherto customary rubber bearings. Such adhesive beads can be designed in a similar manner to the adhesive beads for adhesively bonding windows in vehicle bodies, wherein use may be made of a similar adhesive material as in the adhesive bonding of windows, or of other suitable adhesive materials. The adhesive material which is used in the Applicant's production vehicle with the model designation “i3” for the adhesive bonding of the “drive module” (=“undercarriage”) to the “life module” (=“vehicle body”) may be mentioned as an example of another such adhesive material. However, according to the invention, the auxiliary frame is not fastened solely by use of adhesive beads between the auxiliary frame and the underbody structure, but rather an additional securing structure is provided, on which the auxiliary frame is downwardly supported, i.e. in proportion with the gravity thereof—namely in addition to the previously mentioned adhesive beads—with the interposition of an acoustic insulating layer which, furthermore, can likewise be designed in the form of one or more such adhesive beads. For safety reasons, the securing structure is fastened to the underbody structure of the vehicle body in an integrally bonded manner (for example by welding) and/or non-positively (preferably via screw connections).
In this connection, it should be expressly emphasized that the present invention is in no way restricted to the use of fiber-reinforced plastics for the body or underbody structure and/or the auxiliary frame; on the contrary, each of the components or parts can also be formed by suitable metallic materials. A mixed construction of the individual parts is optionally also possible in such a manner that at least one of the contact surfaces of the auxiliary frame or of the underbody structure is formed by fiber-reinforced plastic with an adhesive bead.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.